Continued from the post > Condensation Issues
Condensation is basically simple. It involves preventing moist air from coming into contact with cold surfaces (ie. surfaces at temperatures below the dew point of air). In practice this can be achieved by:
- Removing moisture laden air (by ventilation) and/or
- Raising the temperature of any cold interior surface to a level above the room air dew point (by heating).
The best way to remove moist air is to use exhaust fans as its source. An electric fan should be installed in the ceilings of the bathrooms and switched on when using showers or baths. To enable the fan to work more effectively, leave a door or window slightly open while the fan is running.
A ceiling vent is recommended over every sink, basin or trough in the house.
More water vapour is normally generated in laundries tan in any other room. Clothes driers should be ducted to the outside air.
A hood fitted with an exhaust fan is recommended over hot plates and stoves as follows:
- The exhaust fan should be at least 200 mm in diameter.
- The distance between the hotplate and hood should be 600 mm, this distance may be increased to 750 mm if absolutely necessary.
- The width and depth of the hood should be preferably the same as the hot plate or stove.
If it is not practical to install a hood, an exhaust fan may be located in the ceiling over the stove and used while cooking.
In rooms where exhaust fans are impracticable (eg. bedrooms) adequate ventilation can be obtained by opening windows.
Remember it is better to ventilate continuously by having all windows slightly open than by opening one window wide for a short time.
In addition to good ventilation, heating can also help to reduce condensation on walls and ceilings. Condensation on window panes and metal window frames, however, is not significantly reduced by heating. This is because glass and metal are good conductors of heat. Any heat which reaches these surfaces does not warm them appreciably as the heat quickly is lost to the outside air.
In very cold climates (and in Australia this can be takes to mean in areas above the snow line), it may be necessary to provide double glazing to raise the temperature of the inner pane.
It is better to provide some continuous background heating rather than short burst of heating. Continuous heating allows wall and ceiling surfaces to warm up and stay warm, which greatly reduces the risk of condensation. On cold days try to keep inside air temperatures at least 5oC higher than outside air temperatures.
The risk of condensation is considerably reduce in any room if walls and ceiling are insulated, because it allows these surfaces to reach a higher temperature. For an existing house it may not be practical to insulate walls, but ceilings can usually be easily insulated. Apart from reducing the risk of condensation and mould growth, insulation will substantially reduce heating costs.
Technical information by Courtesy of CSIRO.
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